The present invention relates to a system for steering rear wheels of a motor vehicle.
A four-wheel steering system for steering rear wheels together with front wheels is known. The rear wheels are steered in the same direction as the front wheels or in the opposite direction to the front wheels in accordance with a steering angle of the front wheels and a vehicle speed of the motor vehicle.
The rear wheels are steered when a driver intentionally turns a steering wheel in order to go round a curve. However, the four-wheel steering system also operates in accordance with behaviors of the vehicle body and the front wheels caused by outside forces and disturbances to steer the rear wheels in spite of the straight-ahead driving. Japanese Patent Application Laid-Open No. 63-125476 discloses a four-wheel steering system for preventing such a malfunction. In the system, hydraulic pressures in right and left chambers of a power cylinder in the front-wheel steering system are respectively detected by a pair of pressure sensors, and the pressure difference between both pressures is calculated by a calculator in order to detect the behavior of the vehicle. Accordingly, swaying of a vehicle caused by a disturbing force such as wind is detected and the rear wheels are steered accordingly to steady the vehicle, although the steering wheel is at a neutral position for straight-ahead driving.
However, since a pair of pressure sensors are provided for producing output signals, an electric control system for processing the output signals becomes complicated in construction.